Prior art straighteners conventionally apply bending loads to the convex side of distortion deflecting the workpiece through the elastic limit to a point where springback results in a part straightened within tolerance. In some cases the elongated workpiece is rotated to bring the high point under one or plural longitudinally spaced rams which deflect the part beyond yield while rotationally stationary on spaced supports. In other cases the shaft may be rotated during deflection with gradual retraction of the deflecting load to achieve automatic straightening within tolerance.
Such prior art straightening through bending has limitations, particularly as applied to brittle materials such as cast iron which are substantially weaker under surface tension than under compression. Cast iron camshafts are a case in point where a high percentage of scrap is encountered from heat treat distortions which exceed the possibility of straightening through bending which subjects the concave surface of distortion to excessive tensile stress during straightening deflection.
The prior art includes attempts to minimize tensile stress during straightening deflection by applying end compressive loading to the workpiece during deflection and thereby exceed the elastic limit on the compression side of the bending load.
While it is known that peening places surface fibers under compressive stress, applicant is unaware of any production straightening method or apparatus which will automatically impose peening blows on a production workpiece as required to achieve straightening action.